Final Report Summary - LUBSEP (Test of advanced lubrication equipment)
Executive Summary:
Although aircraft gas turbines have evolved tremendously in recent years, the lubrication systems have remained largely unchanged. Lubricants are used in aero-engines to reduce friction and wear as well as for cooling and sealing. To meet requirements such as a lower aero-engine oil consumption, while maintaining reliability and lower mass, novel technologies are required.
The EU-funded project 'Test of advanced lubrication equipment' (LubSEP) addressed this challenge by developing an innovative engine oil system (lubrication system). This developed Pump And Separation System (PASS) integrates three critical functions of the aero-engine into a single system. These are the de-oiling and deaeration of the oil-air mixture generated in the engine bearing and the gearbox sumps as well as oil pumping back toward the oil tank.
De-oiling helps remove small oil droplets from the air flow. Poor de-oiling efficiency implies high engine oil consumption that limits flight endurance and increases oil tank weight and size as well as aircraft emissions.
The deaeration function of the scavenge oil removes air bubbles from the oil-air mixture returning to the tank. Poor deaeration efficiency raises problems with cooling and lubrication of the engine roller bearings.
Project partners have also successfully developed and tested a method that is based on radioactive traces to measure very small engine oil consumptions. A newly developed air blower located at the PASS outlet ensures sealing of the engine bearing chambers and efficient air suction through the whole air-oil separation system.
Use of the PASS will considerably simplify the aero-engine lubrication system. The reduction in number of components will lead to a much lighter and more reliable engine oil system. The innovation could also result in more efficient aero-engines that consume less oil and fuel – a boon for the aeronautics industry and the environment.
Project Context and Objectives:
To perform its lubrication task efficiently, the lubrication system of aero-engines is composed of three fluid lines. A feed line includes a volumetric pump for pure oil (quite often a gerotor pump mechanically driven). It brings the oil where it is needed in the aero-engine, for example inside the bearing chambers and onto the bearings themselves. The air-oil mixture created in these bearings and in the gear sumps is then handled in two different lines. A vent line collects an important part of the air flow. It contains small oil droplets that are retrieved in a deoiler. Then, the scavenge lines, composed of several (between 3 and 6) scavenge volumetric pumps, collect an air-oil mixture from the sumps. This mixture can be composed of quite different air/oil ratios and it needs to be pumped back to the oil tank and to be de-aerated. The feed pump must then work again with almost pure oil (at least 95% of oil).
LubSEP is focused on an integrated pump and separator solution (PASS, Pump And Separator System), more specifically on these 3 functions of the lubrication system:
o The deoiling function: it consists in the removal of small oil droplets from the scavenge air flow. A poor deoiling efficiency implies a high engine oil consumption that limits the flight endurance and increases the weight and size of the oil tank. It is also quite harmful for the environment and maybe even for the passengers in the cabin.
o The deaeration of the scavenge oil: it consists in removing the air bubbles from the oil-air mixture returning to the tank. A too low deaeration efficiency negatively impacts the feed pump. Indeed, if too much air enters the feed pump, not enough oil will be distributed to the bearings and major mechanical problems will arise.
o The pumping of the oil from the sump to the oil tank. If oil stagnates in the bearing chamber, it will oxidize due to prolonged contact with the sealing air. The temperature of the oil and of the bearings will also increase rapidly. This also leads to mechanical trouble and increased maintenance costs
Objectives of LubSEP project
The objectives of the LubSEP project are to improve and to quantify the deoiling performance of the PASS, and to ensure the sealing of all bearing chambers of the aero-engine. Therefore, two different aspects of the innovative system/component are studied:
o Develop a radio-traced oil consumption measurement technique to quantify the oil consumption of the PASS,
o Develop an air blower that ensures the sealing efficiency of the bearing chambers and this blower must be integrated with the PASS.
The description and status of each of the work packages WP2, 3 and 4 of LubSEP after the period 3 (at the end) of the project as well as of the test benches that are used to test all developments, alone or integrated together had to be finalized in the different technical reports (deliverables).
Project Results:
An innovative aero-engine sub-system, called PASS (Pump And Separator System), able to simultaneously separate and pump a gas-liquid mixture was developed by ULB in this LubSEP project. It works efficiently and can be used in many applications (nuclear power plants, pulp and paper processing, petroleum extraction, etc.). However, this PASS was especially designed to handle oil-air mixture generated in modern and future aero-engine lubrication systems. This PASS combines three important functions of the scavenge part of aero-engine lubrication systems: deaeration and deoiling of the oil-air mixture generated in the bearing and the gearbox sumps and pumping of the oil towards the tank. These are critical functions in the engine. A poor deoiling efficiency leads to high oil consumption. This reduces the flight endurance, increases the size and weight of the oil tank and has a negative impact on the environment and even maybe on the atmosphere in the passenger cabin. A poor deaeration and pumping characteristics lead to problems in the cooling and the lubrication of the engine bearings. This is all done in the WP4 of this LubSEP project. The tasks related to this WP4 are on line with the planning until the end of this LubSEP project.
To be completely usable in aero-engines, the PASS separation performance needs to be quantified. It is especially difficult to measure the oil consumption of the PASS as it is very low (only a few g/h) and under the form of quite small droplets (< 2 µm in diameter). Therefore, a radio-traced oil consumption measurement method was developed in the WP3. This measurement technique has been developed and efficiently tested already in period 2 of the LubSEP project. In the 3rd period of the project, this technique has been used with the complete PASS integrated with the air blower.
Indeed, an air blower is also required at the outlet of the PASS to ensure an efficient sealing of the engine bearing chambers and air suction through the whole air-oil separation system. This air blower has been designed and CFD computations have been done to define its expected performance. The manufacturing of this blower components and their assembly have also been done with the full characterization tests done on the ENSAM test bench before moving the blower to ULB for the 3rd period of LubSEP, where the blower has been connected to the PASS and tested with it, in a wide range of rotational speeds of the blower and working conditions of the PASS. The experimental results illustrate that the operation of the blower and the PASS is really working quite efficiently. With a refined design, it could be used in aero-engines. As an example, in wind-milling conditions at as low as 2.000 RPM, if the blower is connected with a 2:1 ratio to the engine shaft, the pressure inside the PASS would be reduced by about 2kPa.
However, some mechanical constraints appear as the PASS and the blower are rotating at different speeds. In a more-electric aircraft configurations, this would be the case as the rotational speed of the PASS and of the blower can be fixed independently.
As a general conclusion, the working principle and the operation of these innovative aero-engine lubrication technologies are now well understood and have been efficiently implemented and tested. They can now be designed “on purpose” for different aero-engine working conditions. Also, the principle of combining the separator and the air blower for an aero-engine integration has been proven. It allows a safety margin for the emptying of the roller bearing mixing chamber in the aero-engine in case of wind milling and other critical operating conditions.
Potential Impact:
The absolute necessity to reduce pollutant emissions as well as the future limited availability of fossil fuels will lead to a continuous increase of fuel and oil costs in the coming years. As of today, the fuel and oil costs contribute to about 40 % of the ownership cost of an aero-engine, the airline companies then request drastic reductions of fuel and oil burn (up to 30 %) for the next generation of engines (2015-2017).
A main objective is therefore the reduction of the Thrust Specific Fuel Consumption (TSFC) to reduce fuel costs on one side and the ecological impact of its combustion on the other side. As an example, a variation of 1 % in SFC corresponds to a saving of about 50,000 € per engine. Important improvements to apply on the current aero-engines to meet this objective concern the global architecture of the turbomachinery, the reduction of engine air extraction but also the reduction of the power off-take. The bleeded air as well as the extracted power from the engine shaft can be significantly reduced by developing new advanced technology for the oil air mixture separation system, as the one developed and tested in the LubSEP project.
Oil consumption by aero-engines is a major concern for both ecological but also for aircraft autonomy reasons. During years, the oil air mixture separation technologies have been inherited from past generation engine architectures but disruptive technology is possible in order to reduce largely the oil content in the air at one of the exits of the oil air separation device.
The general challenge of LubSEP has therefore been to develop and improve solutions to test new and innovative oil air separation components and characterize, with a specific instrumentation, the oil content at the exit of the oil separator or breather. The objectives will be also to prove that the new solution adopted for this particular separation device is reliable, with a weight as low as possible, and presenting the minimum impact on SFC and maintenance costs.
The qualification of the test benches developed for these tests has also been a key factor in the success of the project as the different lubrication components need to be put into production later on, based on the test results obtained with the test benches that were developed in this LubSEP project.
The knowledge and product resulting from this investigation are the different lubrication system components to be integrated in any lubrication system of future aero-engines or even on existing engines (retrofitting) in order to reduce the engine TSFC (by a bit less than 1%, e.g. 0,3-0,4%). The need for these devices is considered as critical for the airframe and engine companies in the mean term (replacement of the present mid range aircraft engines in the period 2015-2018 and development of a new engine generation in the period 2022-2025).
Different dissemination activities have been made during this project and a PhD in Engineering Sciences has been obtained by one of the participants to this research project. Also, thanks to the technical skills and the test expertise developed in this LubSEP project, ULB joined the team of the FP7 Level 2 E-BREAK project where it participates to two WP that are closely related with activities of this LubSEP project.
List of Websites:
http://atm.ulb.ac.be
patrick.hendrick@ulb.ac.be
oberten@ulb.ac.be
Although aircraft gas turbines have evolved tremendously in recent years, the lubrication systems have remained largely unchanged. Lubricants are used in aero-engines to reduce friction and wear as well as for cooling and sealing. To meet requirements such as a lower aero-engine oil consumption, while maintaining reliability and lower mass, novel technologies are required.
The EU-funded project 'Test of advanced lubrication equipment' (LubSEP) addressed this challenge by developing an innovative engine oil system (lubrication system). This developed Pump And Separation System (PASS) integrates three critical functions of the aero-engine into a single system. These are the de-oiling and deaeration of the oil-air mixture generated in the engine bearing and the gearbox sumps as well as oil pumping back toward the oil tank.
De-oiling helps remove small oil droplets from the air flow. Poor de-oiling efficiency implies high engine oil consumption that limits flight endurance and increases oil tank weight and size as well as aircraft emissions.
The deaeration function of the scavenge oil removes air bubbles from the oil-air mixture returning to the tank. Poor deaeration efficiency raises problems with cooling and lubrication of the engine roller bearings.
Project partners have also successfully developed and tested a method that is based on radioactive traces to measure very small engine oil consumptions. A newly developed air blower located at the PASS outlet ensures sealing of the engine bearing chambers and efficient air suction through the whole air-oil separation system.
Use of the PASS will considerably simplify the aero-engine lubrication system. The reduction in number of components will lead to a much lighter and more reliable engine oil system. The innovation could also result in more efficient aero-engines that consume less oil and fuel – a boon for the aeronautics industry and the environment.
Project Context and Objectives:
To perform its lubrication task efficiently, the lubrication system of aero-engines is composed of three fluid lines. A feed line includes a volumetric pump for pure oil (quite often a gerotor pump mechanically driven). It brings the oil where it is needed in the aero-engine, for example inside the bearing chambers and onto the bearings themselves. The air-oil mixture created in these bearings and in the gear sumps is then handled in two different lines. A vent line collects an important part of the air flow. It contains small oil droplets that are retrieved in a deoiler. Then, the scavenge lines, composed of several (between 3 and 6) scavenge volumetric pumps, collect an air-oil mixture from the sumps. This mixture can be composed of quite different air/oil ratios and it needs to be pumped back to the oil tank and to be de-aerated. The feed pump must then work again with almost pure oil (at least 95% of oil).
LubSEP is focused on an integrated pump and separator solution (PASS, Pump And Separator System), more specifically on these 3 functions of the lubrication system:
o The deoiling function: it consists in the removal of small oil droplets from the scavenge air flow. A poor deoiling efficiency implies a high engine oil consumption that limits the flight endurance and increases the weight and size of the oil tank. It is also quite harmful for the environment and maybe even for the passengers in the cabin.
o The deaeration of the scavenge oil: it consists in removing the air bubbles from the oil-air mixture returning to the tank. A too low deaeration efficiency negatively impacts the feed pump. Indeed, if too much air enters the feed pump, not enough oil will be distributed to the bearings and major mechanical problems will arise.
o The pumping of the oil from the sump to the oil tank. If oil stagnates in the bearing chamber, it will oxidize due to prolonged contact with the sealing air. The temperature of the oil and of the bearings will also increase rapidly. This also leads to mechanical trouble and increased maintenance costs
Objectives of LubSEP project
The objectives of the LubSEP project are to improve and to quantify the deoiling performance of the PASS, and to ensure the sealing of all bearing chambers of the aero-engine. Therefore, two different aspects of the innovative system/component are studied:
o Develop a radio-traced oil consumption measurement technique to quantify the oil consumption of the PASS,
o Develop an air blower that ensures the sealing efficiency of the bearing chambers and this blower must be integrated with the PASS.
The description and status of each of the work packages WP2, 3 and 4 of LubSEP after the period 3 (at the end) of the project as well as of the test benches that are used to test all developments, alone or integrated together had to be finalized in the different technical reports (deliverables).
Project Results:
An innovative aero-engine sub-system, called PASS (Pump And Separator System), able to simultaneously separate and pump a gas-liquid mixture was developed by ULB in this LubSEP project. It works efficiently and can be used in many applications (nuclear power plants, pulp and paper processing, petroleum extraction, etc.). However, this PASS was especially designed to handle oil-air mixture generated in modern and future aero-engine lubrication systems. This PASS combines three important functions of the scavenge part of aero-engine lubrication systems: deaeration and deoiling of the oil-air mixture generated in the bearing and the gearbox sumps and pumping of the oil towards the tank. These are critical functions in the engine. A poor deoiling efficiency leads to high oil consumption. This reduces the flight endurance, increases the size and weight of the oil tank and has a negative impact on the environment and even maybe on the atmosphere in the passenger cabin. A poor deaeration and pumping characteristics lead to problems in the cooling and the lubrication of the engine bearings. This is all done in the WP4 of this LubSEP project. The tasks related to this WP4 are on line with the planning until the end of this LubSEP project.
To be completely usable in aero-engines, the PASS separation performance needs to be quantified. It is especially difficult to measure the oil consumption of the PASS as it is very low (only a few g/h) and under the form of quite small droplets (< 2 µm in diameter). Therefore, a radio-traced oil consumption measurement method was developed in the WP3. This measurement technique has been developed and efficiently tested already in period 2 of the LubSEP project. In the 3rd period of the project, this technique has been used with the complete PASS integrated with the air blower.
Indeed, an air blower is also required at the outlet of the PASS to ensure an efficient sealing of the engine bearing chambers and air suction through the whole air-oil separation system. This air blower has been designed and CFD computations have been done to define its expected performance. The manufacturing of this blower components and their assembly have also been done with the full characterization tests done on the ENSAM test bench before moving the blower to ULB for the 3rd period of LubSEP, where the blower has been connected to the PASS and tested with it, in a wide range of rotational speeds of the blower and working conditions of the PASS. The experimental results illustrate that the operation of the blower and the PASS is really working quite efficiently. With a refined design, it could be used in aero-engines. As an example, in wind-milling conditions at as low as 2.000 RPM, if the blower is connected with a 2:1 ratio to the engine shaft, the pressure inside the PASS would be reduced by about 2kPa.
However, some mechanical constraints appear as the PASS and the blower are rotating at different speeds. In a more-electric aircraft configurations, this would be the case as the rotational speed of the PASS and of the blower can be fixed independently.
As a general conclusion, the working principle and the operation of these innovative aero-engine lubrication technologies are now well understood and have been efficiently implemented and tested. They can now be designed “on purpose” for different aero-engine working conditions. Also, the principle of combining the separator and the air blower for an aero-engine integration has been proven. It allows a safety margin for the emptying of the roller bearing mixing chamber in the aero-engine in case of wind milling and other critical operating conditions.
Potential Impact:
The absolute necessity to reduce pollutant emissions as well as the future limited availability of fossil fuels will lead to a continuous increase of fuel and oil costs in the coming years. As of today, the fuel and oil costs contribute to about 40 % of the ownership cost of an aero-engine, the airline companies then request drastic reductions of fuel and oil burn (up to 30 %) for the next generation of engines (2015-2017).
A main objective is therefore the reduction of the Thrust Specific Fuel Consumption (TSFC) to reduce fuel costs on one side and the ecological impact of its combustion on the other side. As an example, a variation of 1 % in SFC corresponds to a saving of about 50,000 € per engine. Important improvements to apply on the current aero-engines to meet this objective concern the global architecture of the turbomachinery, the reduction of engine air extraction but also the reduction of the power off-take. The bleeded air as well as the extracted power from the engine shaft can be significantly reduced by developing new advanced technology for the oil air mixture separation system, as the one developed and tested in the LubSEP project.
Oil consumption by aero-engines is a major concern for both ecological but also for aircraft autonomy reasons. During years, the oil air mixture separation technologies have been inherited from past generation engine architectures but disruptive technology is possible in order to reduce largely the oil content in the air at one of the exits of the oil air separation device.
The general challenge of LubSEP has therefore been to develop and improve solutions to test new and innovative oil air separation components and characterize, with a specific instrumentation, the oil content at the exit of the oil separator or breather. The objectives will be also to prove that the new solution adopted for this particular separation device is reliable, with a weight as low as possible, and presenting the minimum impact on SFC and maintenance costs.
The qualification of the test benches developed for these tests has also been a key factor in the success of the project as the different lubrication components need to be put into production later on, based on the test results obtained with the test benches that were developed in this LubSEP project.
The knowledge and product resulting from this investigation are the different lubrication system components to be integrated in any lubrication system of future aero-engines or even on existing engines (retrofitting) in order to reduce the engine TSFC (by a bit less than 1%, e.g. 0,3-0,4%). The need for these devices is considered as critical for the airframe and engine companies in the mean term (replacement of the present mid range aircraft engines in the period 2015-2018 and development of a new engine generation in the period 2022-2025).
Different dissemination activities have been made during this project and a PhD in Engineering Sciences has been obtained by one of the participants to this research project. Also, thanks to the technical skills and the test expertise developed in this LubSEP project, ULB joined the team of the FP7 Level 2 E-BREAK project where it participates to two WP that are closely related with activities of this LubSEP project.
List of Websites:
http://atm.ulb.ac.be
patrick.hendrick@ulb.ac.be
oberten@ulb.ac.be